In a signal supply apparatus such as might find use in an electro-optical device, signals that are supplied from multiple digital-to-analog converters are subject to impedance conversion by respective voltage followers, and provided as outputs to control the operation of the device. The housing includes LEDs for each port to monitor the condition of the signals. The memory cell’s channel region has a cross-section at right angles to a direction along the channel length, the width W and height H of which are each less than or equal to 10 nm. A filter script is applied to the user interface definition to provide a filtered user interface definition. A system embodiment includes an interface to receive merchandising information from a plurality of sources, the merchandising information being related to a plurality of buyers; and a social recommendation engine to process the merchandising information to identify related buyers, and to notify a user of a related buyer based on the merchandising information.